Mosquitoes are vectors for disease in human beings and animals. These insects carry diseases such as malaria, heartworm, dengue fever, encephalitis, yellow fever and West Nile virus, causing millions of human deaths around the world every year.
Mosquitoes in the genus Anopheles are the principle vectors of malaria. Malaria is a devastating infectious disease caused by Plasmodium spp. that results in approximately 660,000 deaths per year. Recent evidence indicates that malaria probably causes double this number of deaths because it debilitates children and leaves them susceptible to fatal bacterial diseases such as pneumonia, bacteraemia and encephalitis.
Plasmodium falciparum, the cause of the most virulent form of malaria, has developed resistance to currently used drugs. This in turn has led to an increase in the incidence of malaria and to fewer drugs for both treatment and prophylaxis of the disease.
Aedes aegypti is the main vector of the viruses that cause Yellow fever and Dengue. Other viruses, the causal agents of various types of encephalitis, Zika virus and Chikungunya are also carried by Aedes spp. mosquitoes. Wuchereria bancrofti and Brugia malayi, parasitic roundworms that cause filariasis, are usually spread by mosquitoes in the genera Culex, Mansonia, and Anopheles. 
In addition to spread of disease, mosquitoes biting humans constitutes a significant nuisance and loss of amenity and may cause economic losses due to effects on tourism and leisure activities. Thus, chemical attractants and repellants remain an important tool for reducing mosquito bites and the resulting rates of infection and spread of disease.
Female mosquitoes choose their mammalian hosts based in part on complex chemical cues. Some of these signals, such as carbon dioxide, have been well characterized on a molecular level. For example, carbon dioxide is not only a potent mosquito stimulant but also augments mosquito feeding behaviors and modulates attraction to other human body odors. Thus, carbon dioxide has been used previously as an effective tool against infection. However, Anopheles gambiae strains that lack functional CO2 receptors are still capable of locating human hosts, indicating that additional chemical signals also drive host preference. Further, logistical issues can make the provision of carbon dioxide difficult, in particular in low resource areas.
There is a therefore a need to provide formulations for affecting the behaviour of mosquitoes.